Sulfur-hydrocarbon slurry pipeline transportation containing an inorganic corrosion inhibitor

ABSTRACT

A process for preventing plugging and corrosion of conduits used in making and transporting sulfur in the form of a sulfur-liquid hydrocarbon slurry by addition prior to, during, or after preparation of the slurry of a small amount of ammonium polysulfide or ammonium hydrosulfide.

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Horvath June 3, 1975 [54] SULFUR-HYDROCARBON SLURRY 3,331,657 7/1967 Peter et al. 302/66 PIPELINE TRANSPORTATION 3,438,680 Srclhevermanm 302/66 CONTAINING AN INORGANIC CORROSION 970 gggf INHIBITOR 3,547,496 12/1970 Kruka 302/66 75 Inventor: Richard Horvath, Houston, Tex. 3,547,497 12/1970 Bolger 302/66 3,606,482 9/1971 Vondrak 302/66 [73] Assignee: Shell Oil Company, Houston, Tex. 3,606,483 9/ 1971 Gable et a]. 302/66 [22] Filed: Jan. 8, 1973 [21] APPL 321,885 Primary ExaminerBenjamin R. Padgett Assistant Examinerlrwin Gluck Related Appllcatlon Data Attorney, Agent, or FirmFredrik Marlowe [63] Continuation-impart of Ser. No. 36,994, May 13,

1970, abandoned.

[52} US. Cl 21/25 R; 21/2.'7 R; 208/47; [57] ABSTRACT 208/236; 252/387; P 302/14; 302/66 A process for preventing plugging and corrosion of [51] lhit. C1. 1B65g 33/04; C231 11/16 conduits used in making and transporting Sulfur i the 158] Fleld of S 2 7 302/14 form of a sulfur-liquid hydrocarbon slurry by addition 21/2-5 R; 208/47' 236 prior to, during, or after preparation of the slurry of a small amount of ammonium polysulfide or ammonium [56] References Cited hydrosulfide.

lJNITED STATES PATENTS 2,798,772 7/1957 Redcay 302/ 14 2 Claims, No Drawings SULFUR-HYDROCARBON SLURRY PIPELINE TRANSPORTATION CONTAINING AN INORGANIC CORROSION INHIBITOR CROSS-REFERENCE TO RELATED PATENT APPLICATION This is a continuation-in-part of application Ser. No. 36,994, filed May 13, 1970, and now abandoned.

BACKGROUND OF THE INVENTION The transportation of sulfur neat or as a water or oil slurry in pipelines is well known in the art as noted by reference to US. Pat. Nos. 2,798,772; 2,917,345 or 3,947,578, or as described in Pipeline Industry, June, 1967, pages 58-60. In making the sulfur into a sulfurhydrocarbon slurry, the sulfur is generally sprayed in molten form into either water or a hydrocarbon to form a slurry suitable for transportation through a pipeline. Formation of a stable slurry wherein the sulfur does not undergo any undesirable change, cause corrosion, or does not exhibit a tendency to wide variation in viscosity is essential to the process. In addition other problems may be encountered during preparation and transportation of the slurry through a pipeline. Thus, separation of the sulfur from the carrier fluid, plating or coating of the sulfur on equipment and pipeline walls causing plugging of the pipeline, corrosion, viscosity changes due to pressure and temperature variations encountered requiring increases in pumping power which increases operation costs, etc., are only a few of the problems normally encountered in making sulfurliquid hydrocarbon slurries for transporting through pipelines.

Although the above are serious problems for consideration in making and transporting sulfur slurries through pipelines, nevertheless, the transportation of sulfur in slurry form through pipelines is an effective, attractive and economic means of transportation, particularly since sulfur is recovered or obtained from iso' lated, remote and inaccessible areas, and must be transported to desired accessible areas. As noted above, a number of methods have been proposed for making sulfur slurries for pipeline transportation such as injecting molten sulfur into water or a liquid hydrocarbon. Such sulfur slurries when transported through pipelines generally do not overcome the corrosion, coating and lor plugging problems described above.

OBJECTS OF THE INVENTION An object of the present invention is to prepare for pipeline transportation 21 sulfur-liquid hydrocarbon slurry which is stable, flowable and non-corrosive.

Another object of the present invention is to transport through a pipeline sulfur-liquid hydrocarbon slur ries without causing sulfur coating, deposition or plugging or corrosion of the pipeline.

Still another object of the invention is to form a slurry of sulfur in a liquid hydrocarbon medium, which when formed is stable, non-corrosive, does not tend to cause corrosion of preparatory equipment and pipelines and does not cause plugging when the slurry is transported through a pipeline and from which the sulfur can be readily recovered as essentially pure sulfur at the terminal end of the line.

Another object is to transfer sulfur as a liquid hydrocarbon slurry by pipeline over great distances under non-corrosive conditions and at reduced pumping and handling costs.

Other objects will be apparent from the following description.

SUMMARY OF THE INVENTION The present invention is directed essentially to an improved, novel technique for preparing and transporting a sulfur-liquid hydrocarbon slurry through conduits such as pipelines generally over great distances without causing corrosion, coating, deposition or plugging of the slurry equipment, pipeline, etc., due to the tendency of sulfur under such conditions to adhere to equipment and the pipeline walls because of temperature, pressure and other variable conditions so as to corrode and plug said lines by admixing, adding or injecting prior to, during, or after preparation of the sulfur-liquid hydrocarbon slurry or injection into a sulfurliquid hydrocarbon slurry after it has been injected into a pipeline, a small amount of from about 0.01% to about 10% or higher by weight based on the total slurry, preferably between about 0.1% to about 5% by weight, of an aqueous solution of about 0.1% to about 40% by weight or higher of ammonium hydrosulfide or ammonium polysulfide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It has been found that by injecting or adding about 0.1 to 5% by weight based on the total slurry of an ammonium polysulfide solution or ammonium hydrosulfide solution during or after preparation of a sulfurhydrocarbon slurry or into a pipeline transporting a sulfur-liquid hydrocarbon slurry in which the sulfur content of the slurry can vary from about 10% by weight to about 75% by weight or higher, preferably between about 30 and by weight sulfur, results in inhibition of corrosion and prevention of plugging of the line due to sulfur deposition on the walls of the pipeline and results in improved flowability of the slurry through the pipeline at reduced pumping cost. A highly preferred plugging and corrosion preventing composition of this type is a sulfur-liquid hydrocarbon slurry to which is added from about 0.1 to 2% by weight based on the total slurry of a solution of the above concentration of ammonium polysulfide, (NHQ S wherein x and y are integers of at least 2 or more, elg. (NH S wherein y is 2-8, or ammonium hydrosulfide, NH I-IS. The corrosion preventing agent is the ammonium polysulfide and not the ammonium hydrosulfide; however, the ammonium hydrosulfide reacts with free sulfur in the slurry to form the polysulfide. The required concentration of ammonium polysulfide, either added or formed in-situ by reaction of free sulfur in the slurry with added ammonium hydrosulfide, to obtain adequate corrosion inhibition and prevent plugging is dependent primarily upon temperature of the slurry, slurry velocity, etc.

The sulfur-liquid hydrocarbon slurry can be made by any suitable means such as described in US. Pat. Nos. 2,798,772 or 3,443,827. It is preferred that the method for making the sulfur-liquid hydrocarbon slurry be used in which the sulfur is produced in spherical form since this facilitates the stable dispersion and suspension of the sulfur in the liquid hydrocarbon carrier and inhibits attrition and reduces friction. The phase transfer method for making the sulfur slurry as described in US Pat. No. 3,443,827 provides for first forming a sulfur-water slurry and thereafter phase transferring the sulfur particles from the water into a liquid hydrocarbon. In this process the phase transformation to form the sulfur-hydrocarbon slurry can be so controlled that a small amount (1 to by weight basis total slurry) of water is transferred with the sulfur-water phase into the hydrocarbon phase, and thereafter an ammonium hydrosulfide or ammonium polysulfide solution can be added to accomplish the essential desired end of the present invention, namely, corrosion inhibition of sulfur-oil slurries. However, in accordance with the preferred technique of the invention the slurry is formed Table 1 EFFECT OF SULFUR CONTENT OF HIGH STRENGTH AMMONlUM SULFlDE SOLUTIONS ON CORROSION OF CARBON STEEL AT ELEVATED TEMPERATURES Test Conditions Temp., "F 180 180 212 266 Solution Comp. %w

NH: 14.8 33.3 33.3 33.3 H S 12.5 28.1 28.1 28.1 Water Remainder Remainder Remainder Remainder Sulfur, Corrosion Rate, mils/yr" %w Liquid Vapor Liquid Vapor Liquid Vapor Liquid Vapor "'From weight loss and exposure time. No localized attack observed. Sulfur present in solution as polysulfide ion.

Table 2 by direct spraying of molten sulfur into the hydrocarbon.

The hydrocarbon carrier for the sulfur can be any liq uid hydrocarbon ranging from a light petroleum frac' tion such as liquefied petroleum gas (LPG) to fuel oil, gasoline, kerosene, petroleum distillates, condensates, crude oil and mixtures thereof. Preferred are liquid hydrocarbons containing at least 10% by weight or higher of aromatics, preferably about to 30% by weight aromatic enriched kerosene or crude oil or crude oil con densate fractions containing 15 to by weight aromatics which include monoand polyaromatic hydrocarbons.

At the terminal end of the line, the aqueous solution can be readily separated from the sulfur-hydrocarbon system by suitable phase separation, distillation or the like.

Slurries of 40 to 60% by weight of sulfur in (a) an ar omatic (17% by weight) enriched kerosene or (b) a petroleum condensate or (c) a blend of (b) and crude oil or (d) a crude oil slurry, were prepared by (I) spraying molten sulfur directly into the hydrocarbon, for example crude oil at an oil temperature of about 140F, to produce sulfur particles, rather spherical in shape, and with an average size of about 50 microns, or (11) by phase transfer by first injecting molten sulfur into an aqueous liquid such as water and thereafter contacting the slurry thus formed with hydrocarbons (a), (b), (c) or (d) to effect phase transfer of the sulfur particles into the hydrocarbon. After preparation of the sulfuroil slurry, a high strength to NH and 20 to 40% H 5) ammonium polysulfide solution containing EFFECT OF SALT CONTENT OF AMMONIUM POLYSULFIDE SOLUTIONS ON CORROSION OF CARBON STEEL AT ELEVATED TEMPERATURES Test Conditions 'From weight loss and exposure time. No localized attack observed. Basis total solution.

Table 1 indicates the corrosion rate of carbon steel at 266F in a high strength (33%w NH 28%w H 8) ammonium sulfide solution containing various amounts of sulfur present as polysulfide ions. A polysulfide solution containing 0.25%w sulfur was apparently on the borderline for inhibiting corrosion at 266F as evidenced by the wide range in corrosion rate observed (6 to 270 mils/yr). With more sulfur present 0.5%w),

the corrosion rate in the liquid was less than mils/yr at this temperature. ln general, higher strength solutions and higher temperatures require more sulfur present as polysulifde for inhibition of corrosion of carbon steel. When adequate sulfur was present (0.5%w) in the ammonium sulfide, the presence of salt (up to 2.5%w as NaCl) had no effect on its corrosivity to carbon steel (see Table 2).

An advantage of the present process for transporting through pipelines sulfur-liquid hydrocarbon slurries is that the slurry can be also prepared by direct injection of molten sulfur into a suitable liquid hydrocarbon as described in U.S. Pat. No. 2,798,772, and the ammonium polysulfide or ammonium hydrosulfide can be added in the slurry preparation vessel so that a noncorrosive slurry can be injected into the pipeline without additional requirement of ammonium polysulfide or ammonium hydrosulfide injection into the pipeline transporting the slurry. Other processes known to the art can be used to make the sulfur-liquid hydrocarbon slurry depending on the availability of the liquid carriers and slurry preparation conditions.

At the terminal end of the line the water phase can be readily removed by phase separation, and the sulfur can be removed from the liquid hydrocarbon by suitable means such as described in U.S. Pat. No. 2,798,772. The sulfur can be purified by methods as described in US. Pat. Nos. 2,809,885 or 3,489,677 which involves treating oil contaminated sulfur with an aqueous solution containing a mixture of alkali hydrosulfide and corresponding hydroxide, e.g., ammonium hydrosulfide and ammonium hydroxide, or by other suitable means such as recovery of the sulfur from the oil slurry by filtration of molten sulfur and liquid-liquid extraction with a hydrocarbon solvent containing 10 to 50% by weight aromatics. At the receiving terminal the sulfur slurry can be filtered and washed. The recovered sulfur is then melted and purified by liquid-liquid extraction with an aromatic hydrocarbon such as cumene. Also, if desired, the filtered sulfur can be steam stripped to recover bright yellow sulfur.

I claim as my invention:

1. A method for preventing the sulfur corrosion of ferrous materials in contact with a sulfur-hydrocarbon slurry comprising admixing ammonium polysulfide with the slurry, the ammonium polysulfide comprising an aqueous solution of from about 0.01% to about 10% by weight based on total slurry.

2. A method for preventing the sulfur corrosion of ferrous materials in contact with a sulfur-hydrocarbon slurry comprising admixing ammonium polysulfide with the slurry, the ammonium polysulfide being formed at least in part by reacting ammonium hydrosulfide with free sulfur in the slurry, the ammonium hydrosulfide comprising an aqueous solution of from about 0.01% to about 10% by weight based on total slurry. 

1. A METHOD FOR PREVENTING THE SULFUR CORROSION IF FERROUS MATERIALS IN CONTACT WITH A SULFUR-HYDROCARBON SLURRY COMPRISING ADMIXING AMMONIUM POLYSULFIDE WITH THE SLURRY, THE AMMONIUM POLYSULFIDE COMPRISING AN AQUEOUS SOLUTION OF FROM ABOUT 0.01% TO ABOUT 10% BY WEIGHT BASED ON TOTAL SLURRY.
 1. A method for preventing the sulfur corrosion of ferrous materials in contact with a sulfur-hydrocarbon slurry comprising admixing ammonium polysulfide with the slurry, the ammonium polysulfide comprising an aqueous solution of from about 0.01% to about 10% by weight based on total slurry. 